Wavelength-tunable pluggable optical module, optical communication system and wavelength change method of wavelength-tunable pluggable optical module

ABSTRACT

A pluggable electric connector can communicate a communication data signal and a control signal with an optical communication device. An optical signal output unit is configured to be capable of selectively output a wavelength of an optical signal. An optical power adjustment unit can adjust optical power of the optical signal. A pluggable optical receptor can output the optical signal to an optical fiber. A control unit controls a wavelength change operation according to the control signal. The control unit, according to a wavelength change command, commands the optical power adjustment unit to block output of the optical signal, commands the light signal output unit to change the wavelength of the optical signal after the optical signal is blocked, and commands the light signal output unit and the optical power adjustment unit to output the optical signal after the wavelength change operation.

TECHNICAL FIELD

The present invention relates to a wavelength-tunable pluggable opticalmodule, an optical communication system and a wavelength change methodof a wavelength-tunable pluggable optical module.

BACKGROUND ART

In an optical communication system, an optical module used fortransmitting and receiving an optical signal is embedded. For example, awavelength-tunable optical transmission device used in a backup systemof a WDM (Wavelength Division Multiplex) network has been proposed(Patent Literature 1). In the wavelength-tunable optical transmissiondevice, when a wavelength is changed, a controller changes a state of anoptical gate from blocking to passing after the wavelength reaches atarget value and becomes stable. In addition to this, a device with abuilt-in wavelength-tunable light source that blocks an optical outputduring wavelength change (Patent Literature 2), an integrated laserdevice (Patent Literature 3), and a wavelength-tunable optical outputdevice (Patent Literature 4) have been proposed.

Meanwhile, for example, in the optical communication system inconformity with standards such as SFP (Small Form-Factor Pluggable) andXFP, use of the wavelength-tunable pluggable optical module has beendeveloped. The wavelength-tunable pluggable optical module is an opticaltransceiver that is insertable into and removable from a socket of theoptical communication device. When performing a control of thewavelength-tunable pluggable optical module, the wavelength-tunablepluggable optical module receives control information from the opticalcommunication apparatus serving as a host side. Then, operationswitching and changing of the wavelength-tunable pluggable opticalmodule are performed according to the received control information.

In the wavelength-tunable pluggable optical module, there may be a casewhere the wavelength change is requested by the optical communicationdevice. When complying with a request for the wavelength change, thewavelength-tunable pluggable optical module needs to autonomouslyperform and complete the change operation.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Unexamined Patent Application PublicationNo. 2001-268015

[Patent Literature 2] Japanese Unexamined Patent Application PublicationNo. 2004-62105

[Patent Literature 3] Japanese Unexamined Patent Application PublicationNo. 2007-158057

[Patent Literature 4] Japanese Unexamined Patent Application PublicationNo. 2008-28569

SUMMARY OF INVENTION Technical Problem

However, the inventor has found problems described below in theabove-mentioned method. When the wavelength change is performed in thewavelength-tunable pluggable optical module, an unstable optical signaland incorrect wavelength optical signal may be transmitted to an opticaltransmission line due to a gap between timings of change or instabilityof a state of a light source. If the unstable optical signal andincorrect wavelength optical signal are transmitted, the malfunction ofthe communication or the deterioration of the communication quality mayoccur.

Further, in contrast to configurations described in Patent Literatures 1to 4, the wavelength-tunable pluggable optical module has to perform thewavelength change according to a control from an external device servingas a communication host of a system in which the wavelength-tunablepluggable optical module is embedded. Therefore, the wavelength-tunablepluggable optical module has a particular problem where thewavelength-tunable pluggable optical module has to perform thewavelength change of the optical signal while preventing the unstableoptical signal and incorrect wavelength optical signal from beingtransmitted according to the request from the external device.

The present invention has been made in view of the aforementionedcircumstances and aims to prevent transmission of an optical signal toan optical transmission line before a wavelength change operation iscompleted when a wavelength-tunable pluggable optical module isrequested for wavelength change from outside.

Solution to Problem

An aspect of the present invention is a wavelength-tunable pluggableoptical module including: a pluggable electric connector configured tobe capable of communicating a communication data signal and a controlsignal with an optical transmission device, the pluggable electricconnector being insertable into and removable from the opticaltransmission device; an optical signal output unit configured to becapable of selectively outputting a wavelength of an optical signal thatcorresponds to the communication data signal; an optical poweradjustment unit configured to be capable of adjusting optical power ofthe optical signal; a pluggable optical receptor configured to becapable of outputting the optical signal output from the optical poweradjustment unit to an optical fiber, the optical fiber being insertableinto and removable from the pluggable optical receptor; a control unitconfigured to control a wavelength change operation according to thecontrol signal from the pluggable electric connector, in which thecontrol unit, according to a wavelength change command included in thecontrol signal, commands the optical power adjustment unit to blockoutput of the optical signal, commands the optical signal output unit tochange the wavelength of the optical signal after blocking the opticalsignal, and commands the optical power adjustment unit to output theoptical signal after the wavelength change operation.

An aspect of the present invention is a wavelength-tunable pluggableoptical module including: a pluggable electric connector configured tobe capable of communicating a communication data signal and a controlsignal with an optical transmission device, the pluggable electricconnector being insertable into and removable from the opticaltransmission device; an optical signal output unit configured to becapable of selectively outputting a wavelength of a first optical signalthat corresponds to the communication data signal; an optical poweradjustment unit configured to be capable of adjusting optical power ofthe first optical signal; a first pluggable optical receptor configuredto be capable of outputting the first optical signal output from theoptical power adjustment unit to a first optical fiber, the firstoptical fiber being insertable into and removable from the firstpluggable optical receptor; a control unit configured to control awavelength change operation according to the control signal from thepluggable electric connector, a second pluggable optical receptor towhich a second optical signal can be input from a second optical fiber,the second optical fiber being insertable into and removable from thesecond pluggable optical receptor; and an optical reception unitconfigured to be capable of receiving by causing the second opticalsignal input via the second pluggable optical receptor to interfere witha light of a predetermined wavelength, in which the control unit,according to a wavelength change command included in the control signal,commands the optical power adjustment unit to block output of the firstoptical signal, commands the optical signal output unit to change thewavelength of the first optical signal after blocking the first opticalsignal, and commands the optical power adjustment unit to output thefirst optical signal after the wavelength change operation, and theoptical reception unit outputs an electric signal corresponding to thereceived second optical signal to the optical transmission device viathe pluggable electric connector.

An optical communication system including: an optical fiber configuredto transmit an optical signal; a wavelength-tunable pluggable opticalmodule configured to output the optical signal to the optical fiber, theoptical fiber being insertable into and removable from thewavelength-tunable pluggable optical module; and an optical transmissiondevice configured to control the wavelength-tunable pluggable opticalmodule, the wavelength-tunable pluggable optical module being insertableinto and removable from the optical transmission device, in which thewavelength-tunable pluggable optical module includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with the opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of the optical signal that corresponds to the communicationdata signal; an optical power adjustment unit configured to be capableof adjusting optical power of the optical signal; a pluggable opticalreceptor configured to be capable of outputting the optical signaloutput from the optical power adjustment unit to the optical fiber, theoptical fiber being insertable into and removable from the pluggableoptical receptor; and a control unit configured to control a wavelengthchange operation according to the control signal from the pluggableelectric connector, wherein the control unit, according to a wavelengthchange command included in the control signal, commands the opticalpower adjustment unit to block output of the optical signal, commandsthe optical signal output unit to change the wavelength of the opticalsignal after blocking the optical signal, and commands the optical poweradjustment unit to output the optical signal after the wavelength changeoperation.

An aspect of the present invention is an optical communication systemincluding: a first optical fiber and a second optical fiber configuredto transmit an optical signal; a wavelength-tunable pluggable opticalmodule configured to output a first optical signal to the first opticalfiber, a second optical signal being input to the wavelength-tunablepluggable optical module from the second optical fiber, the firstoptical fiber and the second optical fiber being insertable into andremovable from the wavelength-tunable pluggable optical module; and anoptical transmission device configured to control the wavelength-tunablepluggable optical module, the wavelength-tunable pluggable opticalmodule being capable of insertable into and removable from the opticaltransmission device, in which the wavelength-tunable pluggable opticalmodule includes: a pluggable electric connector configured to be capableof communicating a communication data signal and a control signal withthe optical transmission device, the pluggable electric connector beinginsertable into and removable from the optical transmission device; anoptical signal output unit configured to be capable of selectivelyoutputting a wavelength of the first optical signal that corresponds tothe communication data signal; an optical power adjustment unitconfigured to be capable of adjusting optical power of the first opticalsignal; a first pluggable optical receptor configured to be capable ofoutputting the first optical signal output from the optical poweradjustment unit to the first optical fiber, the first optical fiberbeing insertable into and removable from the pluggable optical receptor;a control unit configured to control a wavelength change operationaccording to the control signal from the pluggable electric connector, asecond pluggable optical receptor to which a second optical signal canbe input from a second optical fiber, the second optical fiber beinginsertable into and removable from the second pluggable opticalreceptor; and an optical reception unit configured to be capable ofreceiving by causing the second optical signal input via the secondpluggable optical receptor to interfere with a light of a predeterminedwavelength, wherein the control unit, according to a wavelength changecommand included in the control signal, commands the optical poweradjustment unit to block output of the first optical signal, commandsthe optical signal output unit to change the wavelength of the firstoptical signal after blocking the first optical signal, and commands theoptical power adjustment unit to output the first optical signal afterthe wavelength change operation, and the optical reception unit outputsan electric signal corresponding to the received second optical signalto the optical transmission device via the pluggable electric connector.

An aspect of the present invention is a wavelength change method of awavelength-tunable pluggable optical module including: in thewavelength-tunable pluggable optical module that includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with an opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of an optical signal that corresponds to the communicationdata signal; an optical power adjustment unit configured to be capableof adjusting optical power of the optical signal; and a pluggableoptical receptor configured to be capable of outputting the opticalsignal output from the optical power adjustment unit to an opticalfiber, the optical fiber being insertable into and removable from thepluggable optical receptor; according to a wavelength change commandincluded in the control signal received via the pluggable electricconnector, commanding the optical power adjustment unit to block outputof the optical signal, commanding the optical signal output unit tochange the wavelength of the optical signal after blocking the opticalsignal, and commanding the optical power adjustment unit to output theoptical signal after the wavelength change operation.

An aspect of the present invention is a wavelength change method of awavelength-tunable pluggable optical module including: in awavelength-tunable pluggable optical module that includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with an opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of a first optical signal that corresponds to thecommunication data signal; an optical power adjustment unit configuredto be capable of adjusting optical power of the first optical signal;and a first pluggable optical receptor configured to be capable ofoutputting the first optical signal output from the optical poweradjustment unit to a first optical fiber, the first optical fiber beinginsertable into and removable from the first pluggable optical receptor;a second pluggable optical receptor to which a second optical signal canbe input from a second optical fiber, the second optical fiber beinginsertable into and removable from the second pluggable opticalreceptor; and an optical reception unit configured to be capable ofreceiving by causing the second optical signal input via the secondpluggable optical receptor to interfere with a light of a predeterminedwavelength, causing the optical reception unit to output an electricsignal corresponding to the received second optical signal to theoptical transmission device via the pluggable electric connector,according to a wavelength change command included in the control signalreceived via the pluggable electric connector, commanding the opticalpower adjustment unit to block output of the first optical signal,commanding the optical signal output unit to change the wavelength ofthe first optical signal after blocking the first optical signal, andcommanding the optical power adjustment unit to output the first opticalsignal after the wavelength change operation.

Advantageous Effects of Invention

According to the present invention, it is possible to preventtransmission of an optical signal to an optical transmission line beforea wavelength change operation is completed when a wavelength-tunablepluggable optical module is requested for wavelength change fromoutside.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram schematically illustrating a configuration ofa wavelength-tunable pluggable optical module according to a firstexemplary embodiment;

FIG. 2 is a block diagram illustrating a configuration example of a mainpart of an optical communication system in which the wavelength-tunablepluggable optical module according to the first exemplary embodiment isembedded;

FIG. 3 is a block diagram illustrating a configuration example of anoptical signal output unit according to the first exemplary embodiment;

FIG. 4 is a perspective view when the wavelength-tunable pluggableoptical module according to the first exemplary embodiment is observedfrom a side of an optical fiber;

FIG. 5 is a perspective view when the wavelength-tunable pluggableoptical module according to the first exemplary embodiment is observedfrom a side of an optical communication device;

FIG. 6 is a sequence diagram illustrating a wavelength change operationof the wavelength-tunable pluggable optical module according to thefirst exemplary embodiment;

FIG. 7 is a block diagram schematically illustrating a configuration ofa wavelength-tunable pluggable optical module according to a secondexemplary embodiment;

FIG. 8 is a sequence diagram illustrating a wavelength change operationof the wavelength-tunable pluggable optical module according to thesecond exemplary embodiment;

FIG. 9 is a block diagram schematically illustrating a configuration ofa wavelength-tunable pluggable optical module according to a thirdexemplary embodiment;

FIG. 10 is a block diagram illustrating a configuration example of anoptical reception unit according to the third exemplary embodiment; and

FIG. 11 is a sequence diagram illustrating a wavelength change operationof a reception side of the wavelength-tunable pluggable optical moduleaccording to the third exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

Exemplary embodiments of the present invention will be described belowwith reference to the drawings. The same components are denoted by thesame reference numerals throughout the drawings, and a repeatedexplanation is omitted as needed.

First Exemplary Embodiment

A wavelength-tunable pluggable optical module 100 according to a firstexemplary embodiment will be described. FIG. 1 is a block diagramschematically illustrating a configuration of the wavelength-tunablepluggable optical module 100 according to the first exemplaryembodiment. FIG. 2 is a block diagram illustrating a configurationexample of a main part of an optical communication system 1000 in whichthe wavelength-tunable pluggable optical module 100 according to thefirst exemplary embodiment is embedded. As illustrated in FIG. 2, thewavelength-tunable pluggable optical module 100 is configured to causean optical fiber with connector 91 to be insertable into and removablefrom the wavelength-tunable pluggable optical module 100. For example, aFC type connector or MU type connector can be used for the connector ofthe optical fiber with connector 91. The wavelength-tunable pluggableoptical module 100 is controlled based on a control signal CON1 inputfrom an optical communication device 92 serving as a communication host.Note that the wavelength-tunable pluggable optical module 100 may alsoreceive a data signal with the control signal CON1 from the opticalcommunication device 92. In this case, the wavelength-tunable pluggableoptical module 100 may output an optical signal LS modulated based onthe received data signal. The optical communication device 92 performscommunication data processing such as flaming processing of acommunication data signal from the wavelength-tunable pluggable opticalmodule 100 or a communication data signal input to thewavelength-tunable pluggable optical module 100.

The wavelength-tunable pluggable optical module 100 includes a pluggableelectric connector 11, an optical signal output unit 13, an opticalpower adjustment unit 14, a control unit 12, and a pluggable opticalreceptor 15.

The pluggable electric connector 11 is configured to be insertable intoand removable from the optical communication device 92. The pluggableelectric connector 11 receives the control signal CON1 that is anelectric signal output from the optical communication device 92 andforwards the control signal CON1 to the control unit 12. The pluggableelectric connector 11 may also forward an electric signal output fromthe control unit 12 to the optical communication device 92.

The control unit 12 controls operations of the optical signal outputunit 13 and the optical power adjustment unit 14 based on the controlsignal CON1 input from the optical communication device 92 via thepluggable electric connector 11. Specifically, the control unit 12 canchange a wavelength of the optical signal LS (also referred to as afirst optical signal) output from the optical signal output unit 13 by acontrol signal CON2 output to the optical signal output unit 13.Further, a modulation signal is included in the control signal CON2 andthe optical signal output unit 13 modulates the optical signal LSaccording to the modulation signal. The control unit 12 may also adjustoptical power of the optical signal LS output from the optical poweradjustment unit 14 by a control signal CON 3 output to the optical poweradjustment unit 14.

The optical signal output unit 13 outputs the optical signal LS of apredetermined wavelength modulated by a predetermined modulation method.The wavelength of the optical signal LS output from the optical signaloutput unit 13 is tunable. Thus, the optical signal output unit 13outputs the optical signal LS of a single wavelength within a tunablewavelength range according to the control signal CON2 output from thecontrol unit 12. The optical signal output unit 13 may modulate theoptical signal LS by various types of modulation methods such as phasemodulation, amplitude modulation and polarization modulation or bycombining the various types of modulation methods.

A configuration example of the optical signal output unit 13 will bedescribed. FIG. 3 is a block diagram illustrating the configurationexample of the optical signal output unit 13 according to the firstexemplary embodiment. The optical signal output unit 13 includes awavelength-tunable light source 121 and an optical modulation unit 122.The wavelength-tunable light source 121 includes a semiconductor laserand wavelength tuning means such as a ring oscillator, for example, andoutputs an output light Lorig. The output light Lorig is controlled bythe control signal CON2. A modulation signal MOD the optical modulationunit 122 is a Mach-Zehnder type optical modulator, for example. Notethat, although not illustrated in FIGS. 1 and 2, the optical modulationunit 122 outputs the optical signal LS generated by modulating theoutput light Lorig according to the modulation signal MOD correspondingto the communication data signal input from the optical communicationdevice 92 via the pluggable electric connector 11. For example, themodulation signal MOD is output from a drive circuit which is notillustrated according to the communication data signal input from theoptical communication device 92.

The optical power adjustment unit 14 can adjust the optical power of theoptical signal LS by attenuating or blocking the optical signal LSoutput from the optical signal output unit 13. As described above, theoptical power adjustment unit 14 adjusts the optical power of theoptical signal LS according to the control signal CON3 output from thecontrol unit 12. For example, an optical attenuator may be used as theoptical power adjustment unit 14.

The pluggable optical receptor 15 (also referred to as a first pluggableoptical receptor) is configured to cause the connector of the outsideoptical fiber with connector 91 (also referred to as a first opticaltransmission line) to be insertable into and removable from thepluggable optical receptor 15. The pluggable optical receptor 15transmits the optical signal LS output from the optical power adjustmentunit 14 to the optical fiber 91.

Appearances of the wavelength-tunable pluggable optical module 100 willbe described. FIG. 4 is a perspective view when the wavelength-tunablepluggable optical module 100 according to the first exemplary embodimentis observed from a side of the optical fiber 91. A numerical sign 61shown in FIG. 4 indicates an upper surface of the wavelength-tunablepluggable optical module 100. A numerical sign 62 shown in FIG. 4indicates an entry point of the pluggable optical receptor 15 into whichthe connector of the optical fiber 91 is inserted. FIG. 5 is aperspective view when the wavelength-tunable pluggable optical module100 according to the first exemplary embodiment is observed from a sideof the optical communication device 92. A numerical sign 63 shown inFIG. 5 indicates a lower surface of the wavelength-tunable pluggableoptical module 100. A numerical sign 64 shown in FIG. 5 indicates aconnection part of the pluggable electric connector 11 which isconnected to the optical communication device 92.

Next, a wavelength change operation of the wavelength-tunable pluggableoptical module 100 will be described. FIG. 6 is a sequence diagramillustrating the wavelength change operation of the wavelength-tunablepluggable optical module 100 according to the first exemplaryembodiment.

Step S11: Reception of Wavelength Change Command

In a state where the wavelength-tunable pluggable optical module 100outputs the optical signal LS of the wavelength λ1 to the optical fiber91, the control unit 12 receives the control signal CON1 including awavelength change command for the optical signal from the opticalcommunication device 92.

Step S12: Optical Signal Block Operation

The control unit 12 performs a block operation of the optical signalbased on the wavelength change command. Specifically, the control unit12 commands the optical power adjustment unit 14 to block the opticalsignal LS using the control signal CON3. The optical power adjustmentunit 14 blocks the optical signal LS according to the control signalCON3. The control unit 12 may also perform the block operation of theoptical signal LS by commanding the optical signal output unit 13 tostop outputting the optical signal LS using the control signal CON2.Note that the control unit 12 may also command the optical poweradjustment unit 14 to block the optical signal LS and command theoptical signal output unit 13 to stop outputting the optical signal LSin parallel when performing the block operation of the optical signal.

Step S13: Wavelength Change Command

The control unit 12 commands the optical signal output unit 13 to changethe wavelength of the optical signal LS from λ1 to λ2 (λ1≠λ2) based onthe wavelength change command. Thus, the optical signal output unit 13changes the wavelength of the optical signal LS from λ1 to λ2. In thiscase, the optical signal output unit 13 may perform the operation forchanging the wavelength from λ1 to λ2 after stopping the output of theoptical signal LS.

Step S14: Output Restart Command

After the wavelength change is finished, the control unit 12 performs anoperation for restarting the output of the optical signal LS.Specifically, the control unit 12 controls the optical power adjustmentunit 14 to adjust the optical signal LS to a predetermined opticalpower. Thus, the optical signal LS of the wavelength λ2 is output to theoptical fiber 91.

The control unit 12 may control the optical signal output unit 13 tooutput the optical signal LS of the wavelength λ2 after the wavelengthchange before the control of the optical power adjustment unit 14 in theStep S14 when the output of the optical signal of the optical signaloutput unit 13 has been stopped in the Step S12 or S13.

As described above, the present configuration robustly blocks the outputof the optical signal when the wavelength-tunable pluggable opticalmodule changes the wavelength of the optical signal according to thecommand of the optical communication device 92. Therefore, transmissionof an instable optical signal during the wavelength change can beprevented. Then, the optical signal is transmitted after the wavelengthchange so that the optical signal having a desired wavelength andstability can be transmitted.

Second Exemplary Embodiment

A wavelength-tunable pluggable optical module 200 according to a secondexemplary embodiment will be described. FIG. 7 is a block diagramschematically illustrating a configuration of the wavelength-tunablepluggable optical module 200 according to the second exemplaryembodiment. The wavelength-tunable pluggable optical module 200 has aconfiguration where the control unit 12 of the wavelength-tunablepluggable optical module 100 according to the first exemplary embodimentis replaced with a control unit 16. Note that the wavelength-tunablepluggable optical module 200 may also receive the data signal with thecontrol signal CON1 from the optical communication device 92. In thiscase, the wavelength-tunable pluggable optical module 200 may output theoptical signal LS modulated based on the received data signal. Otherconfiguration of the wavelength-tunable pluggable optical module 200 isthe same as that of the wavelength-tunable pluggable optical module 100,and thereby a description thereof will be omitted.

A wavelength change operation of the control unit 16 is different ascompared with the control unit 12. Hereinafter, the wavelength changeoperation of the wavelength-tunable pluggable optical module 200 will bedescribed. FIG. 8 is a sequence diagram illustrating the wavelengthchange operation of the wavelength-tunable pluggable optical module 200according to the second exemplary embodiment.

Step S21: Reception of Wavelength Change Command

In a state where the wavelength-tunable pluggable optical module 200outputs the optical signal LS of the wavelength λ1 to the optical fiber91, the control unit 16 receives the control signal CON1 including thewavelength change command of the optical signal LS from the opticalcommunication device 92 as in the Step S11 illustrated in FIG. 6.

Step S22: Optical Signal Block Operation

The control unit 16 performs the block operation of the optical signalbased on the wavelength change command as in the Step S12 illustrated inFIG. 6. Specifically, the control unit 16 commands the optical poweradjustment unit 14 to block the optical signal LS using the controlsignal CON3. The optical power adjustment unit 14 blocks the opticalsignal LS according to the control signal CON3. The control unit 16 mayalso perform the block operation of the optical signal LS by commandingthe optical signal output unit 13 to stop outputting the optical signalLS using the control signal CON2. Note that the control unit 16 may alsocommand the optical power adjustment unit 14 to block the optical signalLS and command the optical signal output unit 13 to stop outputting theoptical signal LS in parallel when performing the block operation of theoptical signal LS.

Step S23: Wavelength Change Command

The control unit 16 commands the optical signal output unit 13 to changethe wavelength of the optical signal LS from λ1 to λ2 (λ1≠λ2) based onthe wavelength change command as in the Step S13 illustrated in FIG. 6.Thus, the optical signal output unit 13 changes the wavelength of theoptical signal LS from λ1 to λ2. In this case, it is assumed that theoptical signal output unit 13 performs the operation for changing thewavelength from λ1 to λ2 after stopping the output of the optical signalLS.

After the wavelength change is completed, the control unit 12 may alsoset parameters which are used for modulating the optical signal LS ofthe wavelength λ2 to the optical modulation unit (the optical modulationunit 122 in FIG. 3) disposed in the optical signal output unit 13. Thecontrol unit 12 may perform the parameter setting based on the controlsignal CON1 or autonomously perform it regardless of a signal fromoutside.

Step S24: Wavelength Change Completion Notification

The control unit 16 notifies the optical communication device 92 ofcompletion of the wavelength change operation. Here, the control unit 16outputs a notification signal INF including information for notifying ofthe completion of the wavelength change operation to the opticalcommunication device 92 via the pluggable electric connector 11.

Step S25: Reception of Output Restart Command

The optical communication device 92 receives the notification signal INFincluding the information for notifying of the completion of thewavelength change operation, and commands the control unit 16 to performan output operation of the optical signal by the control signal CON1. Inthis case, the optical communication device 92 may also monitor a stablestate of a device receiving the optical signal LS output from thewavelength-tunable pluggable optical module 200, and command to performthe output operation of the optical signal when the reception of theoptical signal LS can be done.

Step S26: Output Restart Command

The control unit 16 performs an operation for restart outputting theoptical signal LS according to the command for performing the outputoperation of the optical signal from the optical communication device92. Specifically, the control unit 16 controls the optical poweradjustment unit 14 to adjust the optical signal LS to the predeterminedoptical power. Thus, the optical signal LS of the wavelength λ2 isoutput to the optical fiber 91.

The control unit 16 may control the optical signal output unit 13 tooutput the optical signal LS of the wavelength λ2 after the wavelengthchange before the control of the optical power adjustment unit 14 in theStep S26 when the output of the optical signal of the optical signaloutput unit 13 has been stopped in the Step S22 or S23.

As described above, as in the case of the wavelength-tunable pluggableoptical module 100, the present configuration robustly blocks the outputof the optical signal when the wavelength-tunable pluggable opticalmodule changes the wavelength of the optical signal according to thecommand from the optical communication device 92. Therefore, thetransmission of the instable optical signal during the wavelength changecan be prevented. Then, the optical signal is transmitted after thewavelength change so that the optical signal having the desiredwavelength and stability can be transmitted.

Further, according to the present configuration, the outside opticalcommunication device 92 monitors a progress of the wavelength change andcommands to restart outputting the optical signal after the wavelengthchange is completed. Therefore, the transmission of the instable opticalsignal during the wavelength change can be more robustly prevented.Furthermore, as described above, the optical communication device 92 maymonitor the stable state of the device receiving the optical signal LSoutput from the wavelength-tunable pluggable optical module 200, andcommand to perform the output operation of the optical signal when thereception of the optical signal LS can be done. In other word, since itis possible to command to restart outputting the optical signalaccording to a timing request of a system in which thewavelength-tunable pluggable optical module 200 is embedded, it ispossible to change the wavelength of the optical signal according to theoperation situation of the entire system.

Third Exemplary Embodiment

A wavelength-tunable pluggable optical module 300 according to a thirdexemplary embodiment will be described. FIG. 9 is a block diagramschematically illustrating a configuration of the wavelength-tunablepluggable optical module 300 according to the third exemplaryembodiment. The wavelength-tunable pluggable optical module 300 has aconfiguration where a pluggable optical receptor 17 and an opticalreception unit 18 are added to the wavelength-tunable pluggable opticalmodule 100 according to the first exemplary embodiment and the opticalsignal output unit 13 and the control unit 12 of the wavelength-tunablepluggable optical module 100 are replaced with an optical signal outputunit 20 and a control unit 19. In the wavelength-tunable pluggableoptical module 300, the optical signal output unit 13, the optical poweradjustment unit 14 and the pluggable optical receptor 15 constitute atransmission side, and the pluggable optical receptor 17 and the opticalreception unit 18 constitute a reception side. Note that thewavelength-tunable pluggable optical module 100 may also receive thedata signal (e.g. a data signal DAT illustrated in FIG. 9) with thecontrol signal CON1 from the optical communication device 92. In thiscase, the wavelength-tunable pluggable optical module 100 may output theoptical signal LS modulated based on the received data signal. Otherconfiguration of the wavelength-tunable pluggable optical module 300 isthe same as that of the wavelength-tunable pluggable optical module 100,and thereby a description thereof will be omitted.

The optical signal output unit 20 includes a wavelength-tunable lightsource 21, an optical demultiplexer 22 and an optical modulation unit23. The wavelength-tunable light source 21 can output lights of pluralwavelengths and selectively output a light of a predeterminedwavelength. The light Lorig output from the wavelength-tunable lightsource 21 is branched by the optical demultiplexer 22, and it is thuspossible to output lights to both of a the transmission side (a lightL1) and the reception side (a local oscillation light LO). Thewavelength-tunable light source 21 can be configured to include such asITLA (Integrable Tunable Laser Assembly) on which a light source devicesuch as a semiconductor laser, a wavelength-tunable device such as aring oscillator and a peripheral electric circuit such as a drivecircuit are integrated, for example. The optical modulation unit 23modulates (phase modulation/amplitude modulation) the light L1 from theoptical demultiplexer 22 to generate the optical signal LS. For example,the optical modulation unit 23 includes such as a Mach-Zehnder typemodulator. The modulation of the optical signal LS is performedaccording to the modulation signal MOD output from the control unit 19via the pluggable electric connector 11 based on the control signalCON1. Note that the branching of the light Lorig is not limited to thebranching by the optical demultiplexer 22, and other optical branchingmeans can be used as appropriate.

The pluggable optical receptor 17 (also referred to as a secondpluggable optical receptor) is a pluggable optical receptor of thereception side and is configured to cause a connector of the opticalfiber with connector 93 (also referred to as a second opticaltransmission line) for the reception to be insertable into and removablefrom the pluggable optical receptor 17. For example, a FC type connectoror MU type connector can be used for the connector of the optical fiberwith connector 93. An optical signal IN (also referred to as a secondoptical signal) is input to the pluggable optical receptor 17 from asource via the optical fiber 93.

The optical reception unit 18 is configured, for example, as a digitalcoherent optical receptor. The optical reception unit 18 converts theoptical signal IN received from the outside via the pluggable opticalreceptor 17 into the data signal DAT that is an electric signal andoutput the data signal DAT to the optical communication device via thepluggable electric connector 11. The optical reception unit 18 is awavelength-tunable optical receptor and is configured to be capable ofupdating setting parameters used for the reception by a control signalCON4 from the control unit 19.

The optical reception unit 18 is an optical receptor performing adigital coherent reception in which a DP-QPSK (Dual-PolarizationQuadrature Phase-Shift Keying) optical signal is demodulated into anelectric signal, for example. FIG. 10 is a block diagram illustrating aconfiguration example of the optical reception unit 18 according to thethird exemplary embodiment. As illustrated in FIG. 10, the opticalreception unit 18 include a polarization beam splitter (referred to as aPBS hereinafter) 31, a PBS 32, 90-degree hybrids 33 and 34,optical/electrical converters (O/Es) 41 to 44, analog to digitalconverters (ADCs) 51 to 54, a digital signal processor (referred to as aDSP hereinafter) 35.

The DP-QPSK optical signal is input to the PBS 31 via the pluggableoptical receptor 17. The PBS 31 splits the input DP-QPSK optical signalinto two polarized components orthogonal to each other. Specifically,the PBS 31 splits the input DP-QPSK optical signal into an x-polarizedcomponent x_(in) and a y-polarized component y_(in) orthogonal to eachother. The x-polarized component x_(in) is input to the 90-degree hybrid33 and the y-polarized component y_(in) is input to the 90-degree hybrid34.

A light from the optical demultiplexer 22 is input to the PBS 32 as thelocal oscillation light. In the present exemplary embodiment, the localoscillation light is a CW (Continuous Wave) light of a predeterminedwavelength. The PBS 32 splits the local oscillation light into twopolarized components orthogonal to each other (an x-polarized componentLO_(x) and a y-polarized component LO_(y)). The x-polarized componentLO_(x) of the local oscillation light is input to the 90-degree hybrid33 and the y-polarized component LO_(y) of the local oscillation lightis input to the 90-degree hybrid 34.

The 90-degree hybrid 33 causes the x-polarized component LO_(x) of thelocal oscillation light and the x-polarized component x_(in) tointerfere with each other to perform a detection, and outputs an I(In-phase) component (hereinafter referred as a x_(in)-I component) andQ (Quadrature) component (hereinafter referred as a x_(in)-Q component)the phase of which is different from that of the I component by 90degrees as detected lights. The 90 degree-hybrid 34 causes they-polarized component LO_(y) of the local oscillation light and they-polarized component y_(in) to interfere with each other to perform thedetection, and outputs an I component (hereinafter referred as ay_(in)-I component) and Q component (hereinafter referred as a y_(in)-Qcomponent) as detected lights.

The optical/electrical converters 41 to 44 photoelectrically convertfour optical signals (the x_(in)-I component, the x_(in)-Q component,the y_(in)-I component and the y_(in)-Q component) output from the90-degree hybrids 33 and 34, respectively. Then the optical/electricalconverters 41 to 44 output the analog electric signals generated by theoptical/electrical conversions to the ADCs 51 to 54. Specifically, theoptical/electrical converter 41 photoelectrically converts the x_(in)-Icomponent and outputs the generated analog electric signal to the ADC51. The optical/electrical converter 42 photoelectrically converts thex_(in)-Q component and outputs the generated analog electric signal tothe ADC 52. The optical/electrical converter 43 photoelectricallyconverts the y_(in)-I component and outputs the generated analogelectric signal to the ADC 53. The optical/electrical converter 44photoelectrically converts the y_(in)-Q component and outputs thegenerated analog electric signal to the ADC 54.

The ADCs 51 to 54 convert the analog electric signals output from theoptical/electrical converters 41 to 44 into digital signals and outputsthe converted digital signals to the DSP 35.

The DSP 35 performs predetermined polarization separation digital signalprocessing on the input digital signals and outputs the data signal DATincluding demodulated signals. The data signal DAT is output to theexternal optical communication device 92 via the pluggable electricconnector 11.

Next, a wavelength change operation of the wavelength-tunable pluggableoptical module 300 will be described. As the wavelength change operationof the transmission side is the same as that of the wavelength changeoperation of the wavelength-tunable pluggable optical module 200illustrated in FIG. 8, redundant descriptions of that will be omitted.

Note that, in the wavelength change operation of the transmission sideof the wavelength-tunable pluggable optical module 300, after thecompletion of the wavelength change corresponding to the Step S23 inFIG. 8, the control unit 19 may set parameters used for modulating theoptical signal of the wavelength λ2 to the optical modulation unit (theoptical modulation unit 23 in FIG. 9) disposed in the optical signaloutput unit 20. The control unit 19 may perform the parameter settingbased on the control signal CON1 or the control unit 19 may autonomouslyperform it regardless of a signal from outside.

The wavelength change operation of the reception side of thewavelength-tunable pluggable optical module 300 will be described. FIG.11 is a sequence diagram illustrating of the wavelength change operationof the reception side of the wavelength-tunable pluggable optical module300 according to the third exemplary embodiment.

Step S31: Reception of Wavelength Change Command

In a state where the optical signal IN of the wavelength λ1 is input tothe wavelength-tunable pluggable optical module 200 from the opticalfiber 93, the control unit 16 receives the control signal CON1 includingthe wavelength change command from the optical communication device 92as in the Step S11 illustrated in FIG. 6. In this case, the opticalcommunication device 92 may autonomously decide the wavelength changeaccording to a communication state or may command the wavelength-tunablepluggable optical module 300 to perform the wavelength change accordingto a request of an external device such as a source.

Step S32: Wavelength Change Command

The control unit 19 commands the wavelength-tunable light source 21 ofthe optical signal output unit 20 to change the wavelength of the outputlight Lorig from λ1 to λ2 (λ1≠λ2) based on the wavelength changecommand. Thus, the wavelength-tunable light source 21 changes thewavelength of the optical signal from λ1 to λ2. In this case, thewavelength-tunable light source 21 performs the operation for changingthe wavelength of the optical signal from λ1 to λ2 after stopping theoutput of the optical signal. Thus, the wavelength of the localoscillation light LO output to the optical reception unit 18 is changedfrom λ1 to λ2.

Step S33: Reception Parameter Update

The control unit 19 updates (or sets) reception parameters that theoptical reception unit 18 uses for receiving the wavelength λ2 after thewavelength change according to the control signal CON4.

Step S34: Reception Restart

The control unit 19 commands the optical reception unit 18 to restartreception of the optical signal IN by the control signal CON4. Inresponse to this, the optical reception unit 18 restarts the receptionof the optical signal IN of the wavelength λ2.

As described above, according to the present configuration, as in thecase of the wavelength-tunable pluggable optical module 100, the outputof the optical signal is robustly blocked when the wavelength-tunablepluggable optical module changes the wavelength of the optical signalaccording to the command from the optical communication device 92.Therefore, the transmission of the instable optical signal during thewavelength change can be prevented. Then, the optical signal istransmitted after the wavelength change is completed so that the opticalsignal having the desired wavelength and stability can be transmitted.

Further, according to the present configuration, the wavelength of thelocal oscillation light used for the detection of the received opticalsignal can be changed. Thus, the optical signal of the desiredwavelength within a wavelength-tunable range can be demodulated.Therefore, the optical signal of a complex modulation method can bereceived.

Further, according to the present configuration, as thewavelength-tunable light source 21 is shared by the transmission sideand the reception side, it is possible to achieve miniaturization of thewavelength-tunable pluggable optical module 300 that is transmission andreception two-in-one type. Note that, in the present exemplaryembodiment, needless to say, the transmission and reception sides mayeach include the wavelength-tunable light source. According to thepresent configuration, a wavelength multiplexed optical signal may bereceived from the pluggable optical receptor 17. In this case, only theoptical signal the wavelength of which interferes with the opticalsignal output from the wavelength-tunable light source 21 in the opticalreception unit 18 is detected. Accordingly, the optical signal of aparticular wavelength can be selectively received from the wavelengthmultiplexed optical signal.

Other Exemplary Embodiments

The present invention is not limited to the above-described exemplaryembodiments, and can be modified as appropriate without departing fromthe scope of the invention. For example, in the exemplary embodimentsdescribed above, the optical communication device 92 also may perform astatus request on the wavelength-tunable pluggable optical module. Inthis case, the control unit of the wavelength-tunable pluggable opticalmodule receives the status request from the optical communication device92 via the pluggable electric connector 11. The control unit of thewavelength-tunable pluggable optical module notifies the opticalcommunication device 92 via the pluggable electric connector 11 of theoperation state of the wavelength-tunable pluggable optical module whenreceiving the status request. Specifically, the control unit of thewavelength-tunable pluggable optical module can notify the opticalcommunication device 92 whether or not the wavelength change operationis running. The control unit of the wavelength-tunable pluggable opticalmodule may also notify the optical communication device 92 whichprocessing stage of each step illustrated in FIG. 6, FIG. 8 and FIG. 11(e.g. a state where the block of the optical signal is completed (theStep S12), a state where the wavelength change is completed (the StepS13), etc.) is running during the wavelength change operation. Further,it is possible to notify the optical communication device 92 ofoperation stability information of the wavelength-tunable light sourceand the optical modulation unit included in the optical signal outputunit 13.

For example, in the exemplary embodiments described above, it can beassumed that the optical communication device 92 commands thewavelength-tunable pluggable optical module to stop the output of theoptical signal while the wavelength-tunable pluggable optical module isperforming the wavelength change operation. In this case, the controlunit of the wavelength-tunable pluggable optical module receives thecommand to stop the output of the optical signal from the opticalcommunication device 92 via the pluggable electric connector 11.However, since the wavelength-tunable pluggable optical module is underthe wavelength change operation, the wavelength-tunable pluggableoptical module may reject the command to stop the output of the opticalsignal. Therefore, occurrence of malfunction due to the overlappedoperation requests can be prevented. Further, when receiving the commandto stop the optical signal output from the optical communication device92 via the pluggable electric connector 11, the optical signal outputmay be stopped after the wavelength change is completed. Therefore, theoverlapped operation requests can be processed in order and the desiredoperation required by the optical communication device 92 can berobustly performed. Note that it goes without saying that the opticalcommunication device 92 can appropriately command the wavelength-tunablepluggable optical module to start the output of the optical signal andto stop the output of the optical signal.

In the exemplary embodiments described above, it is described that thecontrol unit of the wavelength-tunable pluggable optical module controlsthe wavelength-tunable light source, the optical modulation unit and theoptical power adjustment unit according to the control signal CON1 fromthe optical communication device 92. However, it is merely an example.The control unit of the wavelength-tunable pluggable optical module canautonomously control the wavelength-tunable light source, the opticalmodulation unit and the optical power adjustment unit regardless of thecontrol signal from outside.

In the exemplary embodiments described above, the communication of thecontrol signal can be achieved by applying the technologies such as aMDIO (Management Data Input/Output) or an I2C (Inter-IntegratedCircuit).

In the exemplary embodiments described above, the power of the opticalsignal output from the optical signal output unit may be monitored and,for example, the optical output power of the wavelength-tunable lightsource disposed in the optical signal output unit may befeedback-controlled. In this case, a part of the optical signal outputfrom the optical signal output unit is branched by such as the opticaldemultiplexer and the branched optical signal is monitored by a lightreceiving device such as a photodiode. Then, the control unit canfeedback-control the power of the optical signal output from the opticalsignal output unit by notifying the control unit of the monitoringresult.

In the exemplary embodiments described above, the power of the opticalsignal output from the optical power adjustment unit is monitored and,for example, the optical power of the optical power adjustment unit andthe optical output power of the wavelength-tunable light source disposedin the optical signal output unit may be feedback-controlled. In thiscase, a part of the optical signal output from the optical poweradjustment unit is branched by such as the optical demultiplexer and thebranched optical signal is monitored by the light receiving device suchas the photodiode. Then, the control unit can feedback-control one orboth of the power of the optical signal output from the optical signaloutput unit and the optical power adjusted by the optical poweradjustment unit by notifying the control unit of the monitoring result.

In the wavelength-tunable pluggable optical module 300 according to thethird exemplary embodiment described above, as in the case of thewavelength-tunable pluggable optical module 200 according to the secondexemplary embodiment, the control unit 19 may notify the opticalcommunication device 92 of the completion of the wavelength change(corresponding to the Step S24 in FIG. 8), the optical communicationdevice 92 may command the control unit 19 to restart the output of theoptical signal (corresponding to the Step S25 in FIG. 8), and thecontrol unit 19 may cause the optical signal output unit 20 to restartthe output of the optical signal according to the command to restart theoutput of the optical signal (corresponding to the Step S22 in FIG. 8).

In the exemplary embodiments, the case where the optical reception unit18 receives the DP-QPSK optical signal is described. However, it ismerely an example. For example, it is configured to be able to receiveother modulation signals such as QAM (quadrature amplitude modulation).

While the present invention has been described above with reference toexemplary embodiments, the present invention is not limited to theexemplary embodiments stated above.

(Supplementary note 1) A wavelength-tunable pluggable optical moduleincluding: a pluggable electric connector configured to be capable ofcommunicating a communication data signal and a control signal with anoptical transmission device, the pluggable electric connector beinginsertable into and removable from the optical transmission device; anoptical signal output unit configured to be capable of selectivelyoutputting a wavelength of an optical signal that corresponds to thecommunication data signal; an optical power adjustment unit configuredto be capable of adjusting optical power of the optical signal; apluggable optical receptor configured to be capable of outputting theoptical signal output from the optical power adjustment unit to anoptical fiber, the optical fiber being insertable into and removablefrom the pluggable optical receptor; a control unit configured tocontrol a wavelength change operation according to the control signalfrom the pluggable electric connector, in which the control unit,according to a wavelength change command included in the control signal,commands the optical power adjustment unit to block output of theoptical signal, commands the optical signal output unit to change thewavelength of the optical signal after blocking the optical signal, andcommands the optical power adjustment unit to output the optical signalafter the wavelength change operation.(Supplementary note 2) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 1, in which the control unitnotifies the optical transmission device of information about a state ofthe wavelength change operation, and the control unit commands theoptical power adjustment unit to output the optical signal according toan output command from the optical transmission device.(Supplementary note 3) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 2, in which the control unitnotifies the optical transmission device of the information about thestate of the wavelength change operation according to a request ofstatus information from the optical transmission device.(Supplementary note 4) The wavelength-tunable pluggable optical moduleaccording to any one of the supplementary notes 1 to 3, in which thecontrol unit commands the optical power adjustment unit to stop theoutput of the optical signal according to an output stop command fromthe optical transmission device.(Supplementary note 5) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 4, in which the control unitpreferentially performs the wavelength change operation when the controlunit receives the output stop command while the wavelength changeoperation is running.(Supplementary note 6) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 4 or 5, in which when the controlunit receives the output stop command while the wavelength changeoperation is running, the control unit commands to stop the output ofthe optical signal after the wavelength change is finished.(Supplementary note 7) A wavelength-tunable pluggable optical moduleincluding: a pluggable electric connector configured to be capable ofcommunicating a communication data signal and a control signal with anoptical transmission device, the pluggable electric connector beinginsertable into and removable from the optical transmission device; anoptical signal output unit configured to be capable of selectivelyoutputting a wavelength of a first optical signal that corresponds tothe communication data signal; an optical power adjustment unitconfigured to be capable of adjusting optical power of the first opticalsignal; a first pluggable optical receptor configured to be capable ofoutputting the first optical signal output from the optical poweradjustment unit to a first optical fiber, the first optical fiber beinginsertable into and removable from the first pluggable optical receptor;a control unit configured to control a wavelength change operationaccording to the control signal from the pluggable electric connector, asecond pluggable optical receptor to which a second optical signal canbe input from a second optical fiber, the second optical fiber beinginsertable into and removable from the second pluggable opticalreceptor; and an optical reception unit configured to be capable ofreceiving by causing the second optical signal input via the secondpluggable optical receptor to interfere with a light of a predeterminedwavelength, in which the control unit, according to a wavelength changecommand included in the control signal, commands the optical poweradjustment unit to block output of the first optical signal, commandsthe optical signal output unit to change the wavelength of the firstoptical signal after blocking the first optical signal, and commands theoptical power adjustment unit to output the first optical signal afterthe wavelength change operation, and the optical reception unit outputsan electric signal corresponding to the received second optical signalto the optical transmission device via the pluggable electric connector.(Supplementary note 8) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 7, in which the control unitnotifies the optical transmission device of information about a state ofthe wavelength change operation, and the control unit commands theoptical power adjustment unit to output the first optical signalaccording to an output command from the optical transmission device.(Supplementary note 9) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 8, in which the control unitnotifies the optical transmission device of the information about thestate of the wavelength change operation according to a request ofstatus information from the optical transmission device.(Supplementary note 10) The wavelength-tunable pluggable optical moduleaccording to any one of the supplementary notes 7 to 9, in which thecontrol unit commands the optical power adjustment unit to stop theoutput of the first optical signal according to an output stop commandfrom the optical transmission device.(Supplementary note 11) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 10, in which the control unitpreferentially performs the wavelength change operation when the controlunit receives the output stop command while the wavelength changeoperation is running.(Supplementary note 12) The wavelength-tunable pluggable optical moduleaccording to the supplementary note 10 or 11, in which when the controlunit receives the output stop command while the wavelength changeoperation is running, the control unit commands to stop the output ofthe first optical signal after the wavelength change is finished.(Supplementary note 13) The wavelength-tunable pluggable optical moduleaccording to any one of the supplementary notes 7 to 12, in which theoptical signal output unit includes: a wavelength-tunable light source;an optical demultiplexer configured to branch a light output from thewavelength-tunable light source; and an optical modulation unitconfigured to modulate one of the lights branched by the opticaldemultiplexer to output the first optical signal, and the opticalreception unit causes the other of the lights branched by the opticaldemultiplexer to interfere with the second optical signal to receive thesecond optical signal.(Supplementary note 14) The wavelength-tunable pluggable optical moduleaccording to any one of the supplementary notes 7 to 13, in which thecontrol unit commands a reception setting according to the secondoptical signal to the optical reception unit after the wavelength changeoperation.(Supplementary note 15) The wavelength-tunable pluggable optical moduleaccording to any one of the supplementary notes 7 to 13, in which awavelength multiplexed optical signal including the second opticalsignal can be input to the second pluggable optical receptor from thesecond optical fiber, and the optical reception unit can selectivelyreceive the second optical signal by causing the wavelength multiplexedoptical signal to interfere with the light of the predeterminedwavelength.(Supplementary note 16) An optical communication system including: anoptical fiber configured to transmit an optical signal; awavelength-tunable pluggable optical module configured to output theoptical signal to the optical fiber, the optical fiber being insertableinto and removable from the wavelength-tunable pluggable optical module;and an optical transmission device configured to control thewavelength-tunable pluggable optical module, the wavelength-tunablepluggable optical module being insertable into and removable from theoptical transmission device, in which the wavelength-tunable pluggableoptical module includes: a pluggable electric connector configured to becapable of communicating a communication data signal and a controlsignal with the optical transmission device, the pluggable electricconnector being insertable into and removable from the opticaltransmission device; an optical signal output unit configured to becapable of selectively outputting a wavelength of the optical signalthat corresponds to the communication data signal; an optical poweradjustment unit configured to be capable of adjusting optical power ofthe optical signal; a pluggable optical receptor configured to becapable of outputting the optical signal output from the optical poweradjustment unit to the optical fiber, the optical fiber being insertableinto and removable from the pluggable optical receptor; and a controlunit configured to control a wavelength change operation according tothe control signal from the pluggable electric connector, the controlunit, according to a wavelength change command included in the controlsignal, commands the optical power adjustment unit to block output ofthe optical signal, commands the optical signal output unit to changethe wavelength of the optical signal after blocking the optical signal,and commands the optical power adjustment unit to output the opticalsignal after the wavelength change operation.(Supplementary note 17) The optical communication system according tothe supplementary note 16, in which the control unit notifies theoptical transmission device of information about a state of thewavelength change operation, and the control unit commands the opticalpower adjustment unit to output the optical signal according to anoutput command from the optical transmission device.(Supplementary note 18) The optical communication system according tothe supplementary note 17, in which the control unit notifies theoptical transmission device of the information about the state of thewavelength change operation according to a request of status informationfrom the optical transmission device.(Supplementary note 19) The optical communication system according toany one of the supplementary notes 16 to 18, in which the control unitcommands the optical power adjustment unit to stop the output of theoptical signal according to an output stop command from the opticaltransmission device.(Supplementary note 20) The optical communication system according tothe supplementary note 19, in which the control unit preferentiallyperforms the wavelength change operation when the control unit receivesthe output stop command while the wavelength change operation isrunning.(Supplementary note 21) The optical communication system according tothe supplementary note 19 or 20, in which when the control unit receivesthe output stop command while the wavelength change operation isrunning, the control unit commands to stop the output of the opticalsignal after the wavelength change is finished.(Supplementary note 22) An optical communication system including: afirst optical fiber and a second optical fiber configured to transmit anoptical signal; a wavelength-tunable pluggable optical module configuredto output a first optical signal to the first optical fiber, a secondoptical signal being input to the wavelength-tunable pluggable opticalmodule from the second optical fiber, the first optical fiber and thesecond optical fiber being insertable into and removable from thewavelength-tunable pluggable optical module; and an optical transmissiondevice configured to control the wavelength-tunable pluggable opticalmodule, the wavelength-tunable pluggable optical module being insertableinto and removable from the optical transmission device, in which thewavelength-tunable pluggable optical module includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with the opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of the first optical signal that corresponds to thecommunication data signal; an optical power adjustment unit configuredto be capable of adjusting optical power of the first optical signal; afirst pluggable optical receptor configured to be capable of outputtingthe first optical signal output from the optical power adjustment unitto the first optical fiber, the first optical fiber being insertableinto and removable from the first pluggable optical receptor; a controlunit configured to control a wavelength change operation according tothe control signal from the pluggable electric connector, a secondpluggable optical receptor to which the second optical signal can beinput from the second optical fiber, the second optical fiber beinginsertable into and removable from the second pluggable opticalreceptor; and an optical reception unit configured to be capable ofreceiving by causing the second optical signal input via the secondpluggable optical receptor to interfere with a light of a predeterminedwavelength, wherein the control unit, according to a wavelength changecommand included in the control signal, commands the optical poweradjustment unit to block output of the first optical signal, commandsthe optical signal output unit to change the wavelength of the firstoptical signal after blocking the first optical signal, and commands theoptical power adjustment unit to output the first optical signal afterthe wavelength change operation, and the optical reception unit outputsan electric signal corresponding to the received second optical signalto the optical transmission device via the pluggable electric connector.(Supplementary note 23) The optical communication system according tothe supplementary note 22, in which the control unit notifies theoptical transmission device of information about a state of thewavelength change operation, and the control unit commands the opticalpower adjustment unit to output the first optical signal according to anoutput command from the optical transmission device.(Supplementary note 24) The optical communication system according tothe supplementary note 23, in which the control unit notifies theoptical transmission device of the information about the state of thewavelength change operation according to a request of status informationfrom the optical transmission device.(Supplementary note 25) The optical communication system according toany one of the supplementary notes 22 to 24, in which the control unitcommands the optical power adjustment unit to stop the output of thefirst optical signal according to an output stop command from theoptical transmission device.(Supplementary note 26) The optical communication system according tothe supplementary note 25, in which the control unit preferentiallyperforms the wavelength change operation when the control unit receivesthe output stop command while the wavelength change operation isrunning.(Supplementary note 27) The optical communication system according tothe supplementary note 25 or 26, in which when the control unit receivesthe output stop command while the wavelength change operation isrunning, the control unit commands to stop the output of the firstoptical signal after the wavelength change is finished.(Supplementary note 28) The optical communication system according toany one of the supplementary notes 22 to 27, in which the optical signaloutput unit includes: a wavelength-tunable light source; an opticaldemultiplexer configured to branch a light output from thewavelength-tunable light source; and an optical modulation unitconfigured to modulate one of the lights branched by the opticaldemultiplexer to output the first optical signal; the optical receptionunit causes the other of the lights branched by the opticaldemultiplexer to interfere with the second optical signal to receive thesecond optical signal.(Supplementary note 29) The optical communication system according toany one of the supplementary notes 22 to 28, in which the control unitcommands a reception setting according to the second optical signal tothe optical reception unit after the wavelength change operation.(Supplementary note 30) The optical communication system according toany one of the supplementary notes 22 to 28, in which a wavelengthmultiplexed optical signal including the second optical signal can beinput to the second pluggable optical receptor from the second opticalfiber, and the optical reception unit can selectively receive the secondoptical signal by causing the wavelength multiplexed optical signal tointerfere with the light of the predetermined wavelength.(Supplementary note 31) A wavelength change method of awavelength-tunable pluggable optical module including: in thewavelength-tunable pluggable optical module that includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with an opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of an optical signal that corresponds to the communicationdata signal; an optical power adjustment unit configured to be capableof adjusting optical power of the optical signal; and a pluggableoptical receptor configured to be capable of outputting the opticalsignal output from the optical power adjustment unit to an opticalfiber, the optical fiber being insertable into and removable from thepluggable optical receptor; according to a wavelength change commandincluded in the control signal received via the pluggable electricconnector, commanding the optical power adjustment unit to block outputof the optical signal, commanding the optical signal output unit tochange the wavelength of the optical signal after blocking the opticalsignal, and commanding the optical power adjustment unit to output theoptical signal after the wavelength change operation.(Supplementary note 32) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 31, in which information about a state of thewavelength change operation is notified to the optical transmissiondevice, and the optical power adjustment unit is commanded to output theoptical signal according to an output command from the opticaltransmission device.(Supplementary note 33) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 32, in which the information about the state of thewavelength change operation is notified to the optical transmissiondevice according to a request of status information from the opticaltransmission device.(Supplementary note 34) The wavelength change method of thewavelength-tunable pluggable optical module according to any one of thesupplementary notes 31 to 33, in which the optical power adjustment unitis commanded to stop the output of the optical signal according to anoutput stop command from the optical transmission device.(Supplementary note 35) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 34, in which the wavelength change operation ispreferentially performed when the output stop command is received whilethe wavelength change operation is running.(Supplementary note 36) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 34 or 35, in which when the output stop command isreceived while the wavelength change operation is running, it iscommanded to stop the output of the optical signal.(Supplementary note 37) A wavelength change method of awavelength-tunable pluggable optical module including: in awavelength-tunable pluggable optical module that includes: a pluggableelectric connector configured to be capable of communicating acommunication data signal and a control signal with an opticaltransmission device, the pluggable electric connector being insertableinto and removable from the optical transmission device; an opticalsignal output unit configured to be capable of selectively outputting awavelength of a first optical signal that corresponds to thecommunication data signal; an optical power adjustment unit configuredto be capable of adjusting optical power of the first optical signal;and a first pluggable optical receptor configured to be capable ofoutputting the first optical signal output from the optical poweradjustment unit to a first optical fiber, the first optical fiber beinginsertable into and removable from the first pluggable optical receptor;a second pluggable optical receptor to which a second optical signal canbe input from a second optical fiber, the second optical fiber beinginsertable into and removable from the second pluggable opticalreceptor; and an optical reception unit configured to be capable ofreceiving by causing the second optical signal input via the secondpluggable optical receptor to interfere with a light of a predeterminedwavelength, causing the optical reception unit to output an electricsignal corresponding to the received second optical signal to theoptical transmission device via the pluggable electric connector,according to a wavelength change command included in the control signalreceived via the pluggable electric connector, commanding the opticalpower adjustment unit to block output of the first optical signal,commanding the optical signal output unit to change the wavelength ofthe first optical signal after blocking the first optical signal, andcommanding the optical power adjustment unit to output the first opticalsignal after the wavelength change operation.(Supplementary note 38) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 37, in which information about a state of thewavelength change operation is notified to the optical transmissiondevice, and the optical power adjustment unit is commanded to output thefirst optical signal according to an output command from the opticaltransmission device.(Supplementary note 39) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 38, in which the information about the state of thewavelength change operation is notified to the optical transmissiondevice according to a request of status information from the opticaltransmission device.(Supplementary note 40) The wavelength change method of thewavelength-tunable pluggable optical module according to any one of thesupplementary notes 37 to 39, in which the optical power adjustment unitis commanded to stop the output of the first optical signal according toan output stop command from the optical transmission device.(Supplementary note 41) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 40, in which the wavelength change operation ispreferentially performed when the output stop command is received whilethe wavelength change operation is running.(Supplementary note 42) The wavelength change method of thewavelength-tunable pluggable optical module according to thesupplementary note 40 or 41, in which when the output stop command isreceived while the wavelength change operation is running, it iscommanded to stop the output of the first optical signal.(Supplementary note 43) The wavelength change method of thewavelength-tunable pluggable optical module according to any one of thesupplementary notes 37 to 42, in which the optical signal output unitincludes: a wavelength-tunable light source; an optical demultiplexerconfigured to branch a light output from the wavelength-tunable lightsource; and an optical modulation unit configured to modulate one of thelights branched by the optical demultiplexer to output the first opticalsignal, the optical reception unit causes the other of the lightsbranched by the optical demultiplexer to interfere with the secondoptical signal to receive the second optical signal.(Supplementary note 44) The wavelength change method of thewavelength-tunable pluggable optical module according to any one of thesupplementary notes 37 to 43, in which a reception setting according tothe second optical signal is commanded to the optical reception unitafter the wavelength change operation.(Supplementary note 45) The wavelength change method of thewavelength-tunable pluggable optical module according to any one of thesupplementary notes 37 to 43, in which a wavelength multiplexed opticalsignal including the second optical signal can be input to the secondpluggable optical receptor from the second optical fiber, and theoptical reception unit can selectively receive the second optical signalby causing the wavelength multiplexed optical signal to interfere withthe light of the predetermined wavelength.

The present invention has been described above with reference to theexemplary embodiments, but the present invention is not limited to theabove exemplary embodiments. The configuration and details of thepresent invention can be modified in various ways which can beunderstood by those skilled in the art within the scope of theinvention.

This application is based upon and claims the benefit of priority fromJapanese patent application No. 2015-43203, filed on Mar. 5, 2015, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   11 PLUGGABLE ELECTRIC CONNECTOR-   12, 16, 19 CONTROL UNITS-   13, 20 OPTICAL SIGNAL OUTPUT UNITS-   14 OPTICAL POWER ADJUSTMENT UNIT-   15, 17 PLUGGABLE OPTICAL RECEPTORS-   18 OPTICAL RECEPTION UNIT-   20 OPTICAL SIGNAL OUTPUT UNIT-   21, 121 WAVELENGTH-TUNABLE LIGHT SOURCES-   22 OPTICAL DEMULTIPLEXER-   23, 122 OPTICAL MODULATION UNITS-   31, 32 POLARIZATION BEAM SPLITTERS (PBSs)-   33, 34 90-DEGREE HYBRIDS-   35 DSP-   41 TO 44 OPTICAL/ELECTRICAL CONVERTERS-   51 TO 54 ANALOG TO DIGITAL CONVERTERS (ADCs)-   91, 93 OPTICAL FIBERS-   92 OPTICAL COMMUNICATION DEVICE-   100, 200, 300 WAVELENGTH-TUNABLE PLUGGABLE OPTICAL MODULES-   1000 OPTICAL COMMUNICATION SYSTEM-   CON1 TO CON4 CONTROL SIGNALS-   DAT DATA SIGNAL-   IN OPTICAL SIGNAL-   INF NOTIFICATION SIGNAL-   L1 LIGHT-   LO LOCAL OSCILLATION LIGHT-   LS OPTICAL SIGNAL-   MOD MODULATION SIGNAL

1. A pluggable optical module comprising: an electrical connectorconfigured to connect with a host communication apparatus; an opticalconnector configured to connect an optical fiber with an optical fiberconnector; an optical light source configured to output a firstwavelength light; a modulator configured to modulate the firstwavelength light based on an electric signal received from the hostcommunication apparatus via the electrical connector and output a firstoptical signal; an optical attenuator configured to control power of thefirst optical signal output to the optical fiber via the opticalconnector; a controller configured to perform a wavelength changeoperation in response to a wavelength change command from the hostcommunication apparatus via the electrical connector, wherein thewavelength change operation comprises: the optical attenuator blocks thefirst optical signal; the optical light source changes the firstwavelength light to a second wavelength light after the opticalattenuator blocks the first optical signal; and the optical attenuatoroutputs a second optical signal after the optical light source changesthe first wavelength light to a second wavelength light, the secondoptical signal is the second wavelength light modulated by themodulator.
 2. The pluggable optical module according to claim 1, whereinthe wavelength change operation further comprises the optical lightsource turns off the first wavelength light after the optical attenuatorblocks the optical signal.
 3. The pluggable optical module according toclaim 2, wherein the wavelength change operation further comprises theoptical light source turns on the second wavelength light after theoptical light source changes the first wavelength light to the secondwavelength light.
 4. The pluggable optical module according to claim 1,wherein the controller informs a state of the pluggable optical moduleto the host communication apparatus in response to a request from thehost communication apparatus.
 5. The pluggable optical module accordingto claim 1, wherein the controller informs a completion of thewavelength change operation to the host communication apparatus afterthe optical attenuator outputs the second optical signal.
 6. Thepluggable optical module according to claim 1, further comprising: aoptical splitter configured to split the second wavelength light; and acoherent optical receiver configured to receive a received opticalsignal by an interference with the split second wavelength light.
 7. Thepluggable optical module according to claim 6, wherein the controller isfurther configured to set a configuration of the coherent opticalreceiver after the optical light source changes the first wavelengthlight to a second wavelength light.
 8. A communication systemcomprising: an optical fiber with an optical fiber connector; apluggable optical module; and a host communication apparatus configuredto control the pluggable optical module, wherein the pluggable opticalmodule comprises: an electrical connector configured to connect with thehost communication apparatus; an optical connector configured to connectthe optical fiber with the optical fiber connector; an optical lightsource configured to output a first wavelength light; a modulatorconfigured to modulate the first wavelength light based on an electricsignal received from the host communication apparatus via the electricalconnector and output a first optical signal; an optical attenuatorconfigured to control power of the first optical signal output to theoptical fiber via the optical connector; and a controller configured toperform a wavelength change operation in response to a wavelength changecommand from the host communication apparatus via the electricalconnector, wherein the wavelength change operation comprises: theoptical attenuator blocks the first optical signal; the optical lightsource changes the first wavelength light to a second wavelength lightafter the optical attenuator blocks the first optical signal; and theoptical attenuator outputs a second optical signal after the opticallight source changes the first wavelength light to a second wavelengthlight, the second optical signal is the second wavelength lightmodulated by the modulator.
 9. The communication system according toclaim 8, wherein the wavelength change operation further comprises theoptical light source turns off the first wavelength light after theoptical attenuator blocks the optical signal.
 10. The communicationsystem according to claim 9, wherein the wavelength change operationfurther comprises the optical light source turns on the secondwavelength light after the optical light source changes the firstwavelength light to the second wavelength light.
 11. The communicationsystem according to claim 8, wherein the controller informs a state ofthe pluggable optical module to the host communication apparatus inresponse to a request from the host communication apparatus.
 12. Thecommunication system according to claim 8, wherein the controllerinforms a completion of the wavelength change operation to the hostcommunication apparatus after the optical attenuator outputs the secondoptical signal.
 13. The communication system according to claim 8,further comprising: an optical splitter configured to split the secondwavelength light; and a coherent optical receiver configured to receivea received optical signal by an interference with the split secondwavelength light.
 14. The communication system according to claim 13,wherein the controller is further configured to set a configuration ofthe coherent optical receiver after the optical light source changes thefirst wavelength light to a second wavelength light.
 15. An opticalcommunication method comprising: outputting a first wavelength light;modulating the first wavelength light based on an electric signalreceived from a host communication apparatus via an electrical connectorand outputting a first optical signal; controlling power of the firstoptical signal output to an optical fiber via an optical connector; andperforming a wavelength change operation in response to a wavelengthchange command from the host communication apparatus via the electricalconnector, wherein the wavelength change operation comprises: blockingthe first optical signal; changing the first wavelength light to asecond wavelength light after blocking the first optical signal; andoutputting the second optical signal after changing the first wavelengthlight to a second wavelength light, the second optical signal is thesecond wavelength light modulated by a modulator.
 16. The opticalcommunication method according to claim 15, wherein the wavelengthchange operation further comprises turning off the first wavelengthlight after blocking the optical signal.
 17. The optical communicationmethod according to claim 16, wherein the wavelength change operationfurther comprises turning on the second wavelength light after changingthe first wavelength light to the second wavelength light.
 18. Theoptical communication method according to claim 15, further comprisingof informing a state of the pluggable optical module to the hostcommunication apparatus in response to a request from the hostcommunication apparatus.
 19. The optical communication method accordingto claim 15, further comprising of informing a completion of thewavelength change operation to the host communication apparatus afteroutputting the second optical signal.
 20. The optical communicationmethod according to claim 15, splitting the second wavelength light; andreceiving a received optical signal by an interference with the splitsecond wavelength light.
 21. The optical communication method accordingto claim 15, setting a configuration of a coherent optical receiverafter the optical light source changes the first wavelength light to asecond wavelength light.